Flow over periodic hills geometyry.
Accurate geometry specification for the hill geometry (from crest at x=0 to base at x=54).
The functions below give a spline fit through the points:
0.	28.0
9.0	27.0
14.0	24.0
20.0	19.0
30.0	11.0
40.0	4.0
54.0	0.0

Between x=0. and x=9.
h(x)=min(28.,
       2.800000000000E+01      +0.000000000000E+00*x
      +6.775070969851E-03*x^2  -2.124527775800E-03*x^3 )

Between x=9. and x=14.
h(x)=  2.507355893131E+01      +9.754803562315E-01*x
      -1.016116352781E-01*x^2  +1.889794677828E-03*x^3

Between x=14. and x=20.
h(x)=  2.579601052357E+01      +8.206693007457E-01*x
      -9.055370274339E-02*x^2  +1.626510569859E-03*x^3  

Between x=20. and x=30.
h(x)=  4.046435022819E+01      -1.379581654948E+00*x
      +1.945884504128E-02*x^2  -2.070318932190E-04*x^3

Between x=30. and x=40.
h(x)=  1.792461334664E+01      +8.743920332081E-01*x
      -5.567361123058E-02*x^2  +6.277731764683E-04*x^3

Between x=40. and x=54.
h(x)=max(0., 
       5.639011190988E+01      -2.010520359035E+00*x
       1.644919857549E-02*x^2  +2.674976141766E-05*x^3 )